A method for preparing a composite visible light catalyst from a zinc extraction tailing of a steelmaking furnace dust oxygen pressure sulfuric acid

Abstract

The present application relates to tailings high value utilization technical field, specifically to a kind of method for preparing composite visible light catalyst from zinc extraction tailings of oxygen pressure sulfuric acid zinc extraction of steel furnace dust, comprising the following steps: S100: steel furnace dust is treated by oxygen pressure sulfuric acid leaching;S300: the zinc extraction tailings and carbohydrate are mixed with deionized water and co-hydrolyzed;S200: gradient magnetic field is introduced in the process of co-hydrolysis, and pulse magnetic field is applied, while Fe3O4 seed is added in advance;S400: high pressure device is placed in heating device;S500: high pressure device is taken out from heating device, cooling, and sample is recovered by magnetic separation;S600: deionized water is washed and dried, to obtain composite catalyst.The present application aims at the problem that inert zinc ferrite in steel furnace dust is difficult to decompose, so that zinc and iron resources are difficult to recycle and reuse.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste harmless disposal and resource and high-value utilization technology, specifically a method for preparing a composite visible light catalyst from tailings of steelmaking furnace dust oxygen pressure sulfuric acid extraction of zinc. Background Technology

[0002] Whether it's the long-process converter steelmaking using molten iron as the main raw material or the short-process electric arc furnace steelmaking using scrap steel, the zinc content in the furnace dust generated during the smelting process is gradually increasing due to the continuous rise in scrap steel usage. However, zinc mainly exists in the form of inert zinc ferrite (ZnFe2O4), which seriously affects its recycling.

[0003] Zinc ferrite, due to its stable spinel structure, is difficult to process. Currently, its treatment primarily involves pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes mainly involve carbothermic reduction to separate zinc through volatilization; however, this method generates greenhouse gas carbon dioxide and is energy-intensive. Hydrometallurgical processes utilize sulfuric acid, hydrochloric acid, and nitric acid to co-leach iron and zinc. While this method is less energy-intensive, it suffers from low leaching efficiency and poor zinc-iron separation. Furthermore, these processes still have limitations in the high-value reuse of iron. Given that steelmaking furnace dust contains a large amount of iron, and iron's low cost and good biocompatibility have made it one of the most promising transition metal catalysts, iron-based catalysts exhibit good reactivity and selectivity due to the small atomic radius and variable oxidation and spin states of iron.

[0004] Patent CN202411810853.1 discloses a manganese-zinc ferrite composite magnetic catalyst and its preparation method, comprising the following steps: S1, adding manganese nitrate, zinc nitrate, and ferric nitrate to deionized water and mixing to dissolve, forming a metal ion solution, wherein the molar ratio of manganese nitrate, zinc nitrate, and ferric nitrate is 1:1:4; S2, adding ethylenediaminetetraacetic acid (EDTA) with the same total mass of metal ions as in the metal ion solution to the metal ion solution, stirring to dissolve, and forming a sol; heating and dehydrating the sol to obtain a dry gel, grinding it to obtain a powder from the dry gel; and taking the powder from the dry gel. Manganese-zinc ferrite nanoparticles were obtained after heat treatment of the powder; S3, calcium nitrate, indium nitrate and thioacetamide were dissolved in deionized water to produce CaIn-2S-4; then manganese-zinc ferrite nanoparticles were added to obtain a suspension of the reaction mixture, wherein the molar ratio of calcium nitrate, indium nitrate and thioacetamide was 1:2:8, and the mass ratio of the added manganese-zinc ferrite nanoparticles to CaIn-2S-4 was 70:1 to 10:1; S4, the suspension of the reaction mixture was subjected to hydrothermal reaction, and then subjected to subsequent extraction treatment to obtain a manganese-zinc ferrite composite magnetic catalyst. Patent CN202411817530.5 discloses a photocatalyst and its preparation method, including the following steps: S1: Weigh 0.296g of copper nitrate trihydrate and 0.808g of ferric nitrate nonahydrate, dissolve them together in 50ml of deionized water to obtain solution A; Weigh 6.3g of citric acid and add it to 100ml of deionized water, stir magnetically and heat in a water bath to 80℃ to dissolve it, to obtain a citric acid complexing agent solution with a concentration of 0.3mol / L; S2: Weigh 0.08g of nitrogen-doped carbon nanotubes and add them to step S1. In step S1, the solution A is stirred until homogeneous to obtain mixture B. In step S2, the citric acid complexing agent solution prepared in step S1 is added to mixture B under stirring. The mixture is heated in a water bath at 80°C and stirred for 4-5 hours to form a viscous colloidal solution. In step S4, the colloidal solution from step S3 is placed in an oven at 130°C for a complexation reaction for 12 hours to form a dry gel. The dry gel is then ground and pulverized using a mortar and calcined in a muffle furnace to obtain the CuFe-2O-4@N-CNTs composite catalyst, which is the photocatalyst. These methods utilize the synergistic treatment of variable-valence metal compounds and organic matter to obtain catalysts with excellent effects. However, the raw materials used in these methods are difficult to obtain, and the processes are relatively complex. Therefore, there is an urgent need to propose a photocatalyst preparation method with widely available raw materials and simple processing procedures.

[0005] The problem arises because steelmaking furnace dust contains a large amount of iron, but also contains a significant amount of inert phases such as zinc ferrite, which hinders its further application. For steelmaking furnace dust dominated by the zinc ferrite inert phase, oxygen-pressure sulfuric acid leaching can be used to break down the inert zinc ferrite phase and remove zinc, leaving iron-containing compounds, mainly basic ferric sulfate, which can be co-hydrolyzed with carbohydrates to further produce visible light catalysts. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for preparing a composite visible light catalyst from zinc extraction tailings using oxygen-pressure sulfuric acid extraction from steelmaking furnace dust. This method addresses the difficulty in recycling iron in zinc-containing steelmaking furnace dust due to the presence of the inert zinc ferrite phase. Furthermore, since iron oxides are widely used in the field of catalysts, this invention proposes a method to decompose the inert zinc ferrite phase in steelmaking furnace dust using a wet process, followed by co-hydrolysis of the iron-containing compound basic ferric sulfate with glucose to obtain the Fe-C-based visible light catalyst ironoxides@HTCC.

[0007] A method for preparing a composite visible light catalyst from tailings of sulfuric acid extraction from steelmaking furnace dust includes the following steps:

[0008] S100: Leaching of steelmaking furnace dust with sulfuric acid under oxygen pressure, and obtaining zinc extraction tailings after zinc leaching;

[0009] S200: The wet zinc extraction tailings and carbohydrates are mixed with deionized water and then loaded into a high-pressure device for co-hydrolysis.

[0010] S300: A magnetic field is introduced during the co-hydrolysis process. The magnetic field is a gradient magnetic field with the magnetic field strength increasing from 0.1T at the bottom to 0.5T at the top. The direction of the magnetic field is consistent with the axis of the high-voltage device. A pulsed magnetic field with a frequency of 0.5-5Hz and a pulse duty cycle of 30%-70% is applied. At the same time, 0.1-0.5wt% of Fe3O4 seed crystals are added to the co-hydrolysis system in advance.

[0011] S400: Place the high-pressure device in a heating device for heat preservation;

[0012] S500: The high-pressure device is removed from the heating device and cooled, and then the composite catalyst is recovered by magnetic separation.

[0013] S600: Finally, it was washed with deionized water and dried to obtain the Fe-C based visible light catalyst Ironoxides@HTCC.

[0014] The method provided by this invention first removes zinc from steelmaking furnace dust using oxygen-pressure sulfuric acid leaching, wherein the furnace dust includes converter ash or electric arc furnace ash. Simultaneous separation of zinc and iron through oxygen-pressure sulfuric acid leaching allows for highly selective separation of zinc into the leaching solution, while iron exists primarily in the slag as basic ferric sulfate, which has the potential to act as a polymerization catalyst. Subsequently, the basic ferric sulfate is co-hydrolyzed with carbohydrates to produce iron oxides and hydrothermal carbon. This synergistically generated hydrolysis product exhibits good doping and catalytic effects. This method removes zinc via wet process, followed by co-hydrolysis with glucose to prepare the Fe-C-based visible light catalyst ironoxides@HTCC.

[0015] Optionally, step S100 specifically involves: (1) first adding steelmaking furnace dust and sulfuric acid to the pressurization equipment and stirring; (2) then introducing O2 into the pressurization equipment and adjusting the oxygen partial pressure by controlling the leaching reaction temperature and the pressurization equipment; (3) heating the mixed solution to the set temperature at a certain heating rate while stirring; (4) after a specific reaction time, opening the cooling water valve to cool down the pressurization equipment and release the pressure; (5) filtering the slurry after the reaction to obtain a zinc-containing solution and wet zinc extraction tailings, and washing and drying the wet zinc extraction tailings.

[0016] Optionally, the steelmaking furnace dust mentioned in step (1) is a dust material made by mixing converter ash and electric arc furnace ash in a certain proportion;

[0017] With a sulfuric acid concentration of 1.4-2 mol / L, a leaching temperature of 170-200℃, and a liquid-to-solid ratio of steelmaking furnace dust to sulfuric acid of 10-15 mL / g, ZnFe₂O₄ was effectively decomposed, resulting in a Zn leaching rate of 98.73%. Simultaneously, these conditions promoted the leaching of Fe. 2+ oxidation and Fe 3+ The precipitation of Fe resulted in 84.39% of the Fe remaining in the solid phase as Fe(OH)SO4, thus achieving selective leaching of Zn from steelmaking furnace dust.

[0018] Optionally, the pressurization equipment in step (1) can be a pressurized reactor or an industrial pressurization device.

[0019] Optionally, the oxygen partial pressure in step (2) can be adjusted from 0.0 to 0.2 MPa. The higher the oxygen partial pressure, the lower the zinc content of the resulting wet zinc extraction tailings.

[0020] Optionally, the heating rate in step (3) can be adjusted according to the changes in sulfuric acid concentration and liquid-solid ratio. In this invention, the heating rate is 10-15℃ / min and the stirring rate is 500-600r / min.

[0021] Optionally, the reaction time in step (4) is 90-150 min.

[0022] Optionally, step S200 specifically involves: (6) mixing the wet zinc extraction tailings with carbohydrates in a certain proportion. (7) To make the raw materials more uniformly mixed, they can be ultrasonically treated for 20-30 minutes; the frequency of ultrasonic treatment is 40-50 kHz.

[0023] Optionally, in step (6), the carbohydrate is preferably glucose, then the ratio of wet zinc extraction tailings to glucose is 5-8:4; the mass ratio of wet zinc extraction tailings to deionized water is 1g:20-30mL.

[0024] Optionally, step S400 specifically involves: (8) placing the high-pressure device in a programmable heating and heat preservation device and heating it to 180-200℃ at a heating rate of 10-15℃ / min. (9) In order to make the reaction more complete, it is necessary to keep it at the temperature for 12-16 hours.

[0025] Optionally, step S500 specifically includes: (10) selecting different cooling rates and different cooling conditions to cool the sample; (11) recovering the composite catalyst based on different magnetic properties.

[0026] Preferably, in step (10), the cooling condition can be selected as air cooling with air as the cooling medium; the cooling rate is 5-10℃ / min.

[0027] Optionally, step S600 specifically involves: (12) finally washing it with deionized water and drying it in a forced-air drying oven at 105-110℃ for 12-16h to obtain the Fe-C based visible light catalyst ironoxides@HTCC; the specific surface area of ​​the Fe-C based visible light catalyst ironoxides@HTCC is 50-150m². 2 / g.

[0028] The method for removing zinc from steelmaking furnace dust by oxygen-pressure sulfuric acid leaching to obtain a composite visible light catalyst provided by the present invention has the following advantages:

[0029] (1) Based on in-depth research on the mineral phase composition of steelmaking furnace dust, this invention addresses the problem that the presence of inert zinc ferrite in steelmaking furnace dust makes it difficult to reuse iron resources at a high value. The method of oxygen pressure sulfuric acid leaching of steelmaking furnace dust material destroys the structure of zinc ferrite to separate zinc, leaving a slag phase with basic ferric sulfate as the main component, and co-hydrolyzes it with carbohydrates to obtain a high-value visible light catalyst.

[0030] (2) This invention, while rendering steelmaking furnace dust harmless, utilizes the co-hydrolysis of a slag phase primarily composed of basic ferric sulfate and carbohydrates. The basic ferric sulfate hydrolyzes to iron oxides, and the carbohydrates hydrolyze to hydrothermal carbon. The iron oxides@HTCC generated by the synergistic reaction of these two hydrolysis products has the advantages of good doping and catalytic effects. This invention can render hazardous waste harmless and transform it into a high-value visible light catalyst, achieving both harmless and high-value utilization of hazardous waste, resulting in significant environmental benefits and certain economic benefits.

[0031] (3) In this invention, a gradient magnetic field and a pulsed magnetic field are introduced during the co-hydrolysis process, and Fe3O4 seeds are added, which further enhances the catalytic performance of the Fe-C based visible light catalyst:

[0032] First, the gradient magnetic field and the pulsed magnetic field have a synergistic enhancing effect. The gradient magnetic field, through the spatial difference in magnetic field strength, generates a directional Lorentz force on charged particles in the co-hydrolysis system, accelerating ion migration rates and regulating their distribution paths. This dynamic magnetic field environment can effectively break the diffusion layer limitation in the reaction system, promoting the uniform mixing of iron oxides and glucose molecules in the zinc extraction tailings at the nanoscale, forming a tighter interfacial contact, and providing a kinetic advantage for subsequent doping of iron oxides and hydrothermal carbon (HTCC). The pulsed magnetic field generates periodic electromagnetic disturbances through a time-varying electromagnetic field, inducing micro-eddy current effects within the system. This electromagnetic stirring effect can further enhance the mass transfer process, avoid the formation of local concentration gradients, and reduce energy loss through the pulse intermittent characteristics, achieving dynamic homogenization of the temperature and concentration fields of the reaction system, ensuring the consistency and efficiency of the co-hydrolysis reaction. The directional magnetic field lines of the gradient magnetic field and the alternating characteristics of the pulsed magnetic field together constitute a complex electromagnetic environment, exerting a dual regulation on the crystallization behavior of iron oxides: the magnetic field acts on the crystal growth interface through the Lorentz force, interfering with the orderly deposition of atoms along specific crystal planes, inhibiting excessive growth in a single crystal orientation, and forcing the iron oxides to be uniformly dispersed in the form of nanoscale particles within the hydrothermal carbon framework. The design of aligning the magnetic field direction with the axis of the high-voltage device promotes the formation of chain-like or network-like arrangements of the iron oxide particles along the magnetic field direction, constructing a porous composite structure with magnetic response characteristics. This structure not only provides a larger specific surface area (50-150 m²) for visible light absorption... 2 The process also enhances the separation efficiency of photogenerated electron-hole pairs and reduces recombination losses through magnetic moment orientation alignment. Pre-added Fe3O4 seeds serve as heterogeneous nucleation sites, significantly increasing the nucleation rate of iron oxides by lowering the nucleation activation energy. Fe3O4 seeds and hydrothermal carbon (HTCC) form strong interfacial chemical bonds (such as CO-Fe bonds) through a co-hydrolysis process, constructing an efficient electron transport channel. This heterojunction structure has dual advantages: extended visible light absorption and improved carrier separation efficiency; under magnetic field induction, the magnetic microdomains of the Fe3O4 seeds and the conjugated carbon network of the HTCC form a magneto-electric synergistic field, forcing photogenerated electrons to migrate rapidly from iron oxides to the HTCC, reducing the electron-hole recombination rate, and thus significantly improving the oxidative degradation capacity for organic pollutants. Attached Figure Description

[0033] Figure 1 The XRD patterns of iron oxides@HTCC and HTCC catalysts in Example 1 are shown.

[0034] Figure 2 SEM image of hydrothermal carbon (HTCC) prepared by hydrothermal synthesis of glucose alone;

[0035] Figure 3 Here is a SEM image of the composite catalyst Iron oxides@HTCC from Example 1;

[0036] Figure 4 This is a TEM image of the composite catalyst Iron oxides@HTCC from Example 1;

[0037] Figure 5 This is an EDS element surface distribution map of the region in the TEM image of Example 1. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides a method for removing zinc from steelmaking furnace dust using oxygen-pressure sulfuric acid leaching to obtain a composite visible light catalyst, comprising the following steps: S100: treating steelmaking furnace dust with oxygen-pressure sulfuric acid leaching to obtain zinc extraction tailings; S300: mixing the zinc extraction tailings and carbohydrates with deionized water at a mass ratio of 5-8:4 and then loading the mixture into a high-pressure device for co-hydrolysis; the mass ratio of wet zinc extraction tailings to deionized water is 1g:20-30mL; S200: introducing a magnetic field during the co-hydrolysis process, wherein the magnetic field is a gradient magnetic field, the magnetic field strength increases from 0.1T at the bottom to 0.5T at the top, the magnetic field direction is consistent with the axis of the high-pressure device, and the applied frequency is 0.5-5Hz. A pulsed magnetic field with a pulse duty cycle of 30%-70% is applied, and 0.1-0.5 wt% of Fe3O4 seed crystals are pre-added to the co-hydrolysis system; S400: The high-pressure device is placed in a heating device and heated to 180-200℃ at a heating rate of 10-15℃ / min and held at that temperature for 12-16h; S500: The high-pressure device is removed from the heating device and cooled, and then the composite catalyst is recovered by magnetic separation; S600: Finally, it is washed with deionized water and dried in a forced-air drying oven at 105-110℃ for 12-16h to obtain the Fe-C based visible light catalyst Ironoxides@HTCC.

[0040] In this invention, the oxygen-pressure sulfuric acid leaching treatment in step S100 specifically includes: (1) adding converter ash and sulfuric acid to the pressurizing equipment at a liquid-to-solid ratio of 10-15 mL / g; the steelmaking furnace dust is converter ash or electric arc furnace ash; (2) introducing O2 into the pressurizing equipment to control the oxygen partial pressure in the oxygen-pressure sulfuric acid leaching treatment to be 0.0-0.2 MPa; (3) heating the mixed solution to the leaching reaction temperature of 170-200℃ at a heating rate of 10-15℃ / min, while stirring; (4) after reacting for 90-150 min, opening the cooling water valve to cool down the pressurizing equipment and release the pressure; (5) filtering the slurry after the reaction to obtain a zinc-containing solution and zinc extraction tailings, and washing and drying the zinc extraction tailings.

[0041] The concentration of the sulfuric acid is 1.4-2 mol / L; the stirring rate is 500-600 r / min.

[0042] Step S200 also includes ultrasonically treating the mixture of zinc extraction tailings and carbohydrates for 20-30 minutes, wherein the frequency of the ultrasonic treatment is 40-50 kHz.

[0043] The Fe3O4 seed crystals in step S300 have a particle size of 50-200 nm, and the carbohydrate is preferably glucose.

[0044] In step S500, the cooling method is air cooling using air as the cooling medium, with a cooling rate of 5-10℃ / min.

[0045] The specific surface area of ​​the Fe-C based visible light photocatalyst Ironoxides@HTCC is 50-150 m². 2 / g, the composite catalyst prepared by the method is used for visible light catalytic degradation of organic pollutants.

[0046] The method provided by this invention, through specific process steps and parameter settings, can effectively achieve the treatment of steelmaking furnace dust and the preparation of composite visible light catalysts, and the resulting catalysts have good catalytic performance.

[0047] To further illustrate the present invention, the following detailed description is provided through the examples and comparative examples.

[0048] Example 1

[0049] (1) Add converter ash and sulfuric acid to the pressurization equipment at a liquid-solid ratio of 10 mL / g. The sulfuric acid concentration is 1.4 mol / L, and the steelmaking furnace dust is converter ash. Introduce O2 into the pressurization equipment and control the oxygen partial pressure to 0.2 MPa. Heat the mixed solution to 170°C at a heating rate of 10°C / min and a stirring rate of 500 r / min. After reacting for 90 min, open the cooling water valve to cool down and release the pressure. Filter the slurry after the reaction to obtain a zinc-containing solution and zinc extraction tailings. Wash and dry the zinc extraction tailings. (2) Mix 1.0 g of zinc extraction tailings with 0.8 g of glucose (carbohydrate) and 20 ml of deionized water. Sonicate for 20 minutes (frequency 40 kHz) to obtain a mixture. (3) The mixture was loaded into a high-pressure device, and a gradient magnetic field (0.1T at the bottom and 0.5T at the top) was introduced during the co-hydrolysis process. A pulsed magnetic field with a frequency of 0.5Hz and a pulse duty cycle of 30% was applied, and 0.1wt% of Fe3O4 seed crystals with a particle size of 50nm were added. (4) The high-pressure device was placed in a heating device and heated to 180℃ at a heating rate of 10℃ / min and held at that temperature for 12h. (5) The high-pressure device was removed and air-cooled at a cooling rate of 5℃ / min. The composite catalyst was recovered by magnetic separation. (6) The catalyst was washed with deionized water and dried in a forced-air drying oven at 105℃ for 12h to obtain the Fe-C based visible light catalyst Ironoxides@HTCC.

[0050] Example 2

[0051] (1) Add converter ash and sulfuric acid to the pressurization equipment at a liquid-to-solid ratio of 12 mL / g. The sulfuric acid concentration is 1.7 mol / L, and the steelmaking furnace dust is electric arc furnace ash. Introduce O2 into the pressurization equipment and control the oxygen partial pressure to 0.1 MPa. Heat the mixed solution to 200°C at a heating rate of 12°C / min and a stirring rate of 550 r / min. After reacting for 120 min, open the cooling water valve to cool down and release the pressure. Filter the slurry after the reaction to obtain a zinc-containing solution and zinc extraction tailings. Wash and dry the zinc extraction tailings. (2) Mix the zinc extraction tailings and glucose with deionized water at a mass ratio of 6:4 and sonicate for 25 minutes (frequency 45 kHz) to obtain a mixture. The mass ratio of zinc extraction tailings to deionized water is 1 g: 25 mL. (3) The mixture was loaded into a high-pressure device, and a gradient magnetic field (0.1T at the bottom and 0.5T at the top) was introduced during the co-hydrolysis process. A pulsed magnetic field with a frequency of 3Hz and a pulse duty cycle of 50% was applied, and 0.3wt% of Fe3O4 seed crystals with a particle size of 100nm were added. (4) The high-pressure device was placed in a heating device and heated to 190℃ at a heating rate of 12℃ / min and held at that temperature for 14h. (5) The high-pressure device was removed and air-cooled at a cooling rate of 7℃ / min. The composite catalyst was recovered by magnetic separation. (6) The catalyst was washed with deionized water and dried in a forced-air drying oven at 108℃ for 14h to obtain the Fe-C based visible light catalyst Ironoxides@HTCC.

[0052] Example 3

[0053] (1) Add converter ash and sulfuric acid to the pressurization equipment at a liquid-solid ratio of 15 mL / g, the sulfuric acid concentration is 2 mol / L, and the steelmaking furnace dust is converter ash; introduce O2 into the pressurization equipment and control the oxygen partial pressure to 0 MPa; heat the mixed solution to 180℃ at a heating rate of 15℃ / min, stir at a stirring rate of 600 r / min, react for 150 min, open the cooling water valve to cool down and release the pressure; filter the slurry after reaction to obtain a zinc-containing solution and zinc extraction tailings, wash and dry the zinc extraction tailings. (2) Mix the zinc extraction tailings and glucose with deionized water at a mass ratio of 8:4, and sonicate for 30 minutes (frequency 50 kHz) to obtain a mixture; the mass ratio of zinc extraction tailings to deionized water is 1 g: 30 mL. (3) The mixture was loaded into a high-pressure device, and a gradient magnetic field (0.1T at the bottom and 0.5T at the top) was introduced during the co-hydrolysis process. A pulsed magnetic field with a frequency of 5Hz and a pulse duty cycle of 70% was applied, and 0.5wt% of Fe3O4 seed crystals with a particle size of 200nm were added. (4) The high-pressure device was placed in a heating device and heated to 200℃ at a heating rate of 15℃ / min and held at that temperature for 16h. (5) The high-pressure device was removed and air-cooled at a cooling rate of 10℃ / min. The composite catalyst was recovered by magnetic separation. (6) The catalyst was washed with deionized water and dried in a forced-air drying oven at 110℃ for 16h to obtain the Fe-C based visible light catalyst Ironoxides@HTCC.

[0054] Comparative Example 1

[0055] Compared with Example 1, the magnetic field treatment in step (3) is removed (i.e., the gradient magnetic field and pulse magnetic field are not introduced), while the other steps and parameters are the same as in Example 1.

[0056] Comparative Example 2

[0057] Compared with Example 1, Fe3O4 seed crystals are not added in step (3), while other steps and parameters are the same as in Example 1.

[0058] Experiment: Catalytic degradation rate test of methyl orange by the catalyst

[0059] Experimental methods

[0060] Referring to GB / T27861-2011 "Test Method for Purification of Aqueous Solutions of Photocatalytic Materials", the specific steps are as follows:

[0061] Prepare 200 mL of methyl orange solution with a concentration of 20 mg / L, and take 50 mL of each solution into five 500 mL beakers, labeled as 1 (catalyst of Example 1), 2 (catalyst of Example 2), 3 (catalyst of Example 3), 4 (catalyst of Comparative Example 1), and 5 (catalyst of Comparative Example 2).

[0062] Add 0.1g of the corresponding catalyst to each beaker and stir magnetically for 30 minutes in the dark to allow the catalyst and solution to reach adsorption-desorption equilibrium.

[0063] Irradiate the beaker under a visible light source (a 500W xenon lamp, 10cm above the liquid surface). Take a sample every 30 minutes, filter it through a 0.45μm filter membrane, and measure the absorbance of the filtrate at 464nm to calculate the degradation rate.

[0064] The formula for calculating the degradation rate is: Degradation rate = ((A0-A) / ... t ) / A0)×100%, where A0 is the initial absorbance, A t Let be the absorbance at time t;

[0065] Table 1

[0066]

[0067]

[0068] As shown in Table 1, the degradation rate of methyl orange by the catalysts of Examples 1-3 was significantly higher than that of Comparative Examples 1 and 2, indicating that the magnetic field treatment and the addition of Fe3O4 seeds in the method of the present invention have a promoting effect on improving the catalytic performance of the catalysts.

[0069] Figure 1 The XRD patterns of the Iron oxides@HTCC and HTCC catalysts from Example 1 are shown. The HTCC catalyst exhibits a broad diffraction peak between 10° and 35°, indicating that its main component is amorphous material, possibly due to the hydrothermal carbonization reaction of glucose during the hydrothermal process, generating amorphous hydrothermal carbon. The XRD pattern of Iron oxides@HTCC shows the simultaneous presence of characteristic diffraction peaks of Fe3O4 and Fe2O3, as well as the "bun" peaks of amorphous carbon, indicating that the Fe-C based composite catalyst was successfully prepared through hydrothermal treatment. This method efficiently achieves the goal of harmless treatment of steelmaking furnace dust and high-value reuse of solid waste.

[0070] Figure 2 SEM image of hydrothermal carbon (HTCC) prepared by hydrothermal synthesis of glucose alone; Figure 3 Here is a SEM image of the composite catalyst Ironoxides@HTCC from Example 1; Figure 4 This is a TEM image of the composite catalyst Iron oxides@HTCC from Example 1; Figure 5 The image shows the EDS elemental distribution map of the region in the TEM image of Example 1. A comparison of the images reveals that the catalyst prepared in this invention exhibits a more significant structural improvement compared to hydrothermal carbon (HTCC).

[0071] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A method for preparing a composite visible light catalyst from tailings of sulfuric acid extraction from steelmaking furnace dust, characterized in that, The method includes the following steps: S100: Steelmaking furnace dust is treated with oxygen pressure sulfuric acid leaching to extract zinc and obtain zinc extraction tailings. S200: The zinc extraction tailings and carbohydrates are mixed with deionized water at a mass ratio of 5-8:4 and then loaded into a high-pressure device for co-hydrolysis; the mixing ratio of wet zinc extraction tailings and deionized water is 1g:20-30mL. The carbohydrate is glucose; S300: A magnetic field is introduced during the co-hydrolysis process. The magnetic field is a gradient magnetic field with the magnetic field strength increasing from 0.1T at the bottom to 0.5T at the top. The direction of the magnetic field is consistent with the axis of the high-voltage device. A pulsed magnetic field with a frequency of 0.5-5Hz and a pulse duty cycle of 30%-70% is applied. At the same time, 0.1-0.5wt% of Fe3O4 seed crystals are added to the co-hydrolysis system in advance. S400: Place the high-pressure device in a heating device, heat it to 180-200℃ at a heating rate of 10-15℃ / min, and keep it at that temperature for 12-16 hours; S500: The high-pressure device is removed from the heating device, cooled, and then the composite catalyst is recovered by magnetic separation. S600: Finally, it is washed with deionized water and dried in a forced-air drying oven at 105-110℃ for 12-16h to obtain the Fe-C based visible light catalyst Ironoxides@HTCC.

2. The method according to claim 1, characterized in that, The oxygen-pressure sulfuric acid leaching treatment in step S100 specifically includes: (1) Add steelmaking furnace dust and sulfuric acid to the booster equipment at a liquid-solid ratio of 10-15 mL / g; the steelmaking furnace dust is converter ash or electric arc furnace ash; (2) Introduce O2 into the pressurization equipment to control the oxygen partial pressure in the oxygen pressure sulfuric acid leaching treatment to be 0.0-0.2 MPa; (3) Heat the mixed solution to the leaching reaction temperature of 170-200℃ at a heating rate of 10-15℃ / min, while stirring. (4) After reacting for 90-150 minutes, open the cooling water valve to cool down the pressurization equipment and release the pressure; (5) The slurry after the reaction is filtered to obtain a zinc-containing solution and zinc extraction tailings, and the zinc extraction tailings are washed and dried.

3. The method according to claim 2, characterized in that, The concentration of the sulfuric acid is 1.4-2 mol / L; The stirring rate is 500-600 r / min.

4. The method according to claim 1, characterized in that, Step S200 also includes ultrasonically treating the mixture of zinc extraction tailings and carbohydrates for 20-30 minutes.

5. The method according to claim 4, characterized in that, The frequency of the ultrasonic treatment is 40-50 kHz.

6. The method according to claim 1, characterized in that, The Fe3O4 seed crystals mentioned in step S300 have a particle size of 50-200 nm.

7. The method according to claim 1, characterized in that, In step S500, the cooling method is air cooling using air as the cooling medium, with a cooling rate of 5-10℃ / min.

8. The method according to claim 1, characterized in that, The specific surface area of ​​the Fe-C based visible light catalyst Ironoxides@HTCC is 50-150 m² / g.

9. The composite catalyst prepared by the method according to claim 1 is used for visible light catalytic degradation of organic pollutants.

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